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www.ColoradoClassicBroncos.com - View topic - High speed/under load detonation
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 High speed/under load detonation 
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Post High speed/under load detonation
Ever since I did my tune up back in Mar-Apr timeframe I've had small issues, well I think I'be uncovered the likely culprit and now I need a solution. I'm experiencing detonation while pulling mountain passes or when the engine is in a full load situation. I've already backed the timing WAY off, like 0 degrees and tried premium fuel to reduce the problem, no luck. The tuneup parts were all stock level replacements and I replaced them all since the problem started, cap & rotor, points, wires & plugs, fuel pump. No other engine parts have messed with. So what else could cause detonation, limited fuel supply, dizzy that is failing in some manner, timing issue that isn't related to the basic setting?

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Kirk

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Tue Aug 28, 2012 5:11 pm
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Post Re: High speed/under load detonation
Hook your timing light up and disconnect the vacuum advance. Rev it up to see how much mechanical advance your getting.

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Rob

74 Ranger EFI351w, 4r70w, ARB 5.13 9in, ARB 5.13D44, and a bunch of other goodies. Best of all the family memories.

04 Mustang Cobra, KenneBell 2.2 feeding a lot of boost on E85. Tire shredding machine

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Wed Aug 29, 2012 6:25 am
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Post Re: High speed/under load detonation
Did you remove the dist? Check to verify thast your wires are properly attached and in the correct order. And, as stated, check you advance, w/ out being hooked to a vacuum source.

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Wed Aug 29, 2012 9:05 am
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Post Re: High speed/under load detonation
Kirk you could definitely have an issue in the dizzy. Zoso's Bronco had issues where the mechanical added too much and he had some severe detonation. That's what it looks like you got too.

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Sat Sep 01, 2012 3:44 pm
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Post Re: High speed/under load detonation
I pulled the vacuum (hooked to a ported carb inlet, so it only kicks in when the carb opens up) and revved it up and I've got 20 degrees mech advance, sound about right?

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Mon Sep 03, 2012 11:35 am
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Post Re: High speed/under load detonation
Sound good to me. Now do it with the vacuum advance hooked up and see what you get.

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Rob

74 Ranger EFI351w, 4r70w, ARB 5.13 9in, ARB 5.13D44, and a bunch of other goodies. Best of all the family memories.

04 Mustang Cobra, KenneBell 2.2 feeding a lot of boost on E85. Tire shredding machine

New project: 77 Bronco Ranger, body work and more body work.

Very little left of a 72 durango tan explorer sport


Mon Sep 03, 2012 11:56 am
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Post Re: High speed/under load detonation
Same numbers, no diff hooked up or not. So maybe the vacuum can has failed.

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Mon Sep 03, 2012 2:22 pm
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